Neuroblastoma, a tumor of peripheral neural crest origin, is the third most common tumor of childhood. The broad, longterm objective of this project is to find genes that contribute to tumorigenesis in a multi-step transgenic mouse model for neuroblastoma. The transgenic mouse model to be used in this study is tumor prone. as a result of over-expression of the human MYCN gene in the peripheral neural crest. Since tumorigenesis in the mouse is initiated using a gene relevant to human neuroblastoma, it is likely that the additional genetic lesions which contribute to neuroblastoma formation in the mouse will be in genes relevant to neuroblastoma in children. Using PCR analysis of microsatellite markers, we have identified 6 chromosomal or subchromosomal regions that show consistent abnormalities in mouse tumors. Four of these were syntenic with corresponding regions of abnormality in human neuroblastoma. A region on the proximal part of chromosome 10 was affected in 30% of tumors and has been localized to an interval of less than 16 cM. Over the five years of this award, our goal is to identify the genetic region most amenable to further study, and to find the gene corresponding to that subchromosomal region. In specific aim 1, we will refine our primary screen to further localize the six regions that contributes to neuroblastoma in the mouse. We will also analyze tumors for differentiation, angiogenesis, apoptosis, proliferation, and invasion, to seek biological correlates for specific regions of LOH. We will focus subsequent positional cloning efforts on chromosome 10 unless our refined screens identify a more compelling region. In specific aim 11, we will further characterize a single genetic region which cooperates with MYCN to cause neuroblastoma in the mouse. We will analyze additional tumors and additional microsatellite markers to localize this interval to 1-2 cM a size appropriate for positional cloning. We will then construct a physical map and contig of this region to identify the corresponding genes. Candidate genes will be tested for expression and mutation in mouse tumors. Health Relatedness: Genes identified as important for the malignant progression of neuroblastoma in the mouse can be tested directly for their role in neuroblastoma in humans. Given the poor outcome associated with childhood neuroblastoma, this work has the potential to increase our understanding of the pathogenesis of neuroblastoma, and may result in improved therapies for children with this disorder.